Voltage regulated power supply system
United States Patent 7564230
A voltage regulator for providing a regulated voltage is disclosed. The voltage regulator comprises an error amplifying module and a regulator. The error amplifying module provides a reference voltage, based on an output voltage to be regulated. The regulator provides a regulated output voltage based on the reference voltage. Voltage regulator provides stable output voltage against variations caused by power supply and load with a defined temperature coefficient.
US Patent References:
Voltage regulator for direct current power supply
Steiner - March, 1983 - 4375614
Rapid turn-on voltage regulator
Petty - March, 1986 - 4574232
Amplifiers with effectively zero input capacitance
Bollons - January, 1991 - 4988953
Level converter circuit having two multi-collector transistors for simplifying circuit configuration
Mitsuya et al. - November, 1993 - 5262682
Drive circuit for brushless motor
Izawa et al. - February, 1994 - 5287044
Voltage regulator for direct current power supply
Steiner - March, 1983 - 4375614
Rapid turn-on voltage regulator
Petty - March, 1986 - 4574232
Amplifiers with effectively zero input capacitance
Bollons - January, 1991 - 4988953
Level converter circuit having two multi-collector transistors for simplifying circuit configuration
Mitsuya et al. - November, 1993 - 5262682
Drive circuit for brushless motor
Izawa et al. - February, 1994 - 5287044
Inventors:
Liwinski, Henry (North Wales, PA, US)
Application Number:
11/329449
Publication Date:
07/21/2009
Filing Date:
01/11/2006
View Patent Images:
Export Citation:
Assignee:
Anadigics, Inc. (Warren, NJ, US)
Primary Class:
Other Classes:
323/280, 323/274, 323/273
International Classes:
G05F1/00
Field of Search:
323/313, 323/280, 323/274, 323/273
US Patent References:
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| 6130529 | Secondary output holdover circuit for a switch-mode power supply | October, 2000 | Andres et al. | 323/303 |
| 6150801 | Regulator apparatus | November, 2000 | Schwertlein et al. | 323/280 |
| 6157244 | Power supply independent temperature sensor | December, 2000 | Lee et al. | 327/539 |
| 6184664 | Voltage regulator circuit for suppressing latch-up phenomenon | February, 2001 | Ponzetta | 323/274 |
| 6188211 | Current-efficient low-drop-out voltage regulator with improved load regulation and frequency response | February, 2001 | Rincon-Mora et al. | 323/280 |
| 6201375 | Overvoltage sensing and correction circuitry and method for low dropout voltage regulator | March, 2001 | Larson et al. | 323/277 |
| 6265856 | Low drop BiCMOS/CMOS voltage regulator | July, 2001 | Cali′ et al. | 323/273 |
| 6340852 | Voltage generating circuit capable of stably supplying power supply voltage less than rated voltage | January, 2002 | Mizoguchi | 307/125 |
| 6677736 | Energy recovery system for droop compensation circuitry | January, 2004 | Barnes et al. | 323/280 |
| 7071664 | Programmable voltage regulator configurable for double power density and reverse blocking | July, 2006 | Teggatz et al. | 323/280 |
| 20010033153 | Microelectronic current regulator | October, 2001 | Pohlman | 323/274 |
| 20030013284 | Structure and method for fabricating power combining amplifiers | January, 2003 | Emrick et al. | 438/575 |
Primary Examiner:
Ullah, Akm E.
Assistant Examiner:
Williams, Arun
Attorney, Agent or Firm:
Botjer, William L.
Claims:
I claim:
1. A system for voltage regulation of an output voltage with respect to a reference voltage, the system comprising: an error amplifying module, the error amplifying module comprising a Bipolar Junction Transistor (BJT), a diode, and at least one resistor, the at least one resistor being connected in series with the diode, the error amplifying module amplifying the difference between the reference voltage and a desired value of the output voltage, the reference voltage being the sum of voltages across the BJT and the diode; and a regulator, the regulator comprising a Field Effect Transistor (FET) and a first resistor, the first resistor being connected between the gate and source of the FET, the gate of the FET being further connected to the collector of the BJT , the diode and the at least one resistor being further connected between the base of the BJT and the source of the FET, the emitter of the BJT being further connected to a ground voltage, the regulator regulating variations in the output voltage based on the amplified difference between the reference voltage and the desired value of the output voltage, wherein the reference voltage and the output voltage are available at a junction of the source of the FET, the first resistor and the diode.
2. The system in accordance to claim 1, wherein the BJT is a Heterojunction Bipolar Transistor.
3. The system in accordance to claim 1, wherein the FET is a Pseudomorphic High Electron Mobility Transistor (pHEMT).
4. The system in accordance to claim 1, wherein the error amplifying module further comprises at least one resistor connected between the emitter of the BJT and the ground voltage.
5. The system in accordance to claim 4, wherein the reference voltage is the sum of voltages across the base-emitter junction of the BJT, the diode and the at least one first resistor.
6. The system in accordance to claim 1, wherein the diode is a Zener diode.
7. The system in accordance to claim 1, wherein the error amplifying module further comprises at least one resistor connected in parallel with the diode.
8. The system in accordance to claim 1, wherein the output voltage is temperature dependent, the output voltage being used for biasing bipolar junction transistors.
9. A system for voltage regulation of an output voltage with respect to a reference voltage, the system comprising: an error amplifying module, the error amplifying module comprising a Bipolar Junction Transistor (BJT), a diode, and at least one resistor, the at least one resistor being connected in series with the diode, the error amplifying module amplifying the difference between the reference voltage and a desired value of the output voltage, the reference voltage being the sum of voltages across the BJT and the diode; a regulator, the regulator comprising a Field Effect Transistor (FET) and a first resistor, the first resistor being connected between the gate and source of the FET, the gate of the FET being further connected to the collector of the BJT, the diode and the at least one resistor being further connected between the base of the BJT and the source of the FET, the emitter of the BJT being further connected to a ground voltage, the regulator regulating variations in the output voltage based on the amplified difference between the reference voltage and the desired value of the output voltage, wherein the reference voltage and the output voltage are available at a junction of the source of the FET, the first resistor and the diode; and a switch module, the switch module switching the regulator in on or off state, the switch module comprising a second Field Effect Transistor (FET), the second FET being connected between the drain of the first FET and a power supply, wherein the switching is based on change in drain source current of the second FET by applying an appropriate voltage to the gate of the second FET.
10. The system in accordance to claim 9, wherein the switch module further comprises at least one resistor connected to the gate of the second FET.
11. The system in accordance to claim 9, wherein the BJT is a Heterojunction Bipolar Transistor (HBT).
12. The system in accordance to claim 9, wherein the first FET is a Pseudomorphic High Electron Mobility Transistor (pHEMT).
13. The system in accordance to claim 9, wherein the reference voltage is the sum of voltages across the base-emitter junction of the BJT, the diode and the at least one first resistor.
14. The system in accordance to claim 9, wherein the error amplifying module further comprises at least one resistor connected between the emitter of the BJT and the ground voltage.
15. The system in accordance to claim 9, wherein the diode is a Zener diode.
16. The system in accordance to claim 9, wherein the error amplifying module further comprises at least one resistor connected in parallel with the diode.
17. The system in accordance to claim 9, wherein the second FET is used as a switch.
18. The system in accordance to claim 9, wherein the first FET is used as an amplifier.
19. A voltage regulated power supply system, the voltage regulated power supply system comprising; a voltage regulator, the voltage regulator comprising: an error amplifying module, the error amplifying module comprising a Bipolar Junction Transistor (BJT), a diode, and at least one resistor, the at least one resistor being connected in series with the diode, the error amplifying module amplifying the difference between the reference voltage and a desired value of the output voltage, the reference voltage being the sum of voltages across the BJT and the diode; a regulator, the regulator comprising a Field Effect Transistor (FET) and a first resistor, the first resistor being connected between the gate and source of the FET, the gate of the FET being further connected to the collector of the BJT, the diode and the at least one resistor being further connected between the base of the BJT and the source of the FET, the emitter of the BJT being further connected to a around voltage, the regulator regulating variations in the output voltage based on the amplified difference between the reference voltage and the desired value of the output voltage, wherein the reference voltage and the output voltage are available at a junction of the source of the FET, the first resistor and the diode; and a power amplifying circuit, the power amplifying circuit receiving the regulated voltage from the voltage regulator, the regulated voltage being used for setting a quiescent current of the power amplifying circuit.
20. The system in accordance to claim 19 further including a switch module, the switch module comprising a second field effect transistor (FET) and one or more second resistors, the one or more second resistors being connected to the gate of the second FET in series, the second FET being connected between the drain of the first FET and a power supply, the switch module switching the voltage regulator in on or off state based on the change in drain source current of the second FET by applying an appropriate voltage to the gate of the second FET.
1. A system for voltage regulation of an output voltage with respect to a reference voltage, the system comprising: an error amplifying module, the error amplifying module comprising a Bipolar Junction Transistor (BJT), a diode, and at least one resistor, the at least one resistor being connected in series with the diode, the error amplifying module amplifying the difference between the reference voltage and a desired value of the output voltage, the reference voltage being the sum of voltages across the BJT and the diode; and a regulator, the regulator comprising a Field Effect Transistor (FET) and a first resistor, the first resistor being connected between the gate and source of the FET, the gate of the FET being further connected to the collector of the BJT , the diode and the at least one resistor being further connected between the base of the BJT and the source of the FET, the emitter of the BJT being further connected to a ground voltage, the regulator regulating variations in the output voltage based on the amplified difference between the reference voltage and the desired value of the output voltage, wherein the reference voltage and the output voltage are available at a junction of the source of the FET, the first resistor and the diode.
2. The system in accordance to claim 1, wherein the BJT is a Heterojunction Bipolar Transistor.
3. The system in accordance to claim 1, wherein the FET is a Pseudomorphic High Electron Mobility Transistor (pHEMT).
4. The system in accordance to claim 1, wherein the error amplifying module further comprises at least one resistor connected between the emitter of the BJT and the ground voltage.
5. The system in accordance to claim 4, wherein the reference voltage is the sum of voltages across the base-emitter junction of the BJT, the diode and the at least one first resistor.
6. The system in accordance to claim 1, wherein the diode is a Zener diode.
7. The system in accordance to claim 1, wherein the error amplifying module further comprises at least one resistor connected in parallel with the diode.
8. The system in accordance to claim 1, wherein the output voltage is temperature dependent, the output voltage being used for biasing bipolar junction transistors.
9. A system for voltage regulation of an output voltage with respect to a reference voltage, the system comprising: an error amplifying module, the error amplifying module comprising a Bipolar Junction Transistor (BJT), a diode, and at least one resistor, the at least one resistor being connected in series with the diode, the error amplifying module amplifying the difference between the reference voltage and a desired value of the output voltage, the reference voltage being the sum of voltages across the BJT and the diode; a regulator, the regulator comprising a Field Effect Transistor (FET) and a first resistor, the first resistor being connected between the gate and source of the FET, the gate of the FET being further connected to the collector of the BJT, the diode and the at least one resistor being further connected between the base of the BJT and the source of the FET, the emitter of the BJT being further connected to a ground voltage, the regulator regulating variations in the output voltage based on the amplified difference between the reference voltage and the desired value of the output voltage, wherein the reference voltage and the output voltage are available at a junction of the source of the FET, the first resistor and the diode; and a switch module, the switch module switching the regulator in on or off state, the switch module comprising a second Field Effect Transistor (FET), the second FET being connected between the drain of the first FET and a power supply, wherein the switching is based on change in drain source current of the second FET by applying an appropriate voltage to the gate of the second FET.
10. The system in accordance to claim 9, wherein the switch module further comprises at least one resistor connected to the gate of the second FET.
11. The system in accordance to claim 9, wherein the BJT is a Heterojunction Bipolar Transistor (HBT).
12. The system in accordance to claim 9, wherein the first FET is a Pseudomorphic High Electron Mobility Transistor (pHEMT).
13. The system in accordance to claim 9, wherein the reference voltage is the sum of voltages across the base-emitter junction of the BJT, the diode and the at least one first resistor.
14. The system in accordance to claim 9, wherein the error amplifying module further comprises at least one resistor connected between the emitter of the BJT and the ground voltage.
15. The system in accordance to claim 9, wherein the diode is a Zener diode.
16. The system in accordance to claim 9, wherein the error amplifying module further comprises at least one resistor connected in parallel with the diode.
17. The system in accordance to claim 9, wherein the second FET is used as a switch.
18. The system in accordance to claim 9, wherein the first FET is used as an amplifier.
19. A voltage regulated power supply system, the voltage regulated power supply system comprising; a voltage regulator, the voltage regulator comprising: an error amplifying module, the error amplifying module comprising a Bipolar Junction Transistor (BJT), a diode, and at least one resistor, the at least one resistor being connected in series with the diode, the error amplifying module amplifying the difference between the reference voltage and a desired value of the output voltage, the reference voltage being the sum of voltages across the BJT and the diode; a regulator, the regulator comprising a Field Effect Transistor (FET) and a first resistor, the first resistor being connected between the gate and source of the FET, the gate of the FET being further connected to the collector of the BJT, the diode and the at least one resistor being further connected between the base of the BJT and the source of the FET, the emitter of the BJT being further connected to a around voltage, the regulator regulating variations in the output voltage based on the amplified difference between the reference voltage and the desired value of the output voltage, wherein the reference voltage and the output voltage are available at a junction of the source of the FET, the first resistor and the diode; and a power amplifying circuit, the power amplifying circuit receiving the regulated voltage from the voltage regulator, the regulated voltage being used for setting a quiescent current of the power amplifying circuit.
20. The system in accordance to claim 19 further including a switch module, the switch module comprising a second field effect transistor (FET) and one or more second resistors, the one or more second resistors being connected to the gate of the second FET in series, the second FET being connected between the drain of the first FET and a power supply, the switch module switching the voltage regulator in on or off state based on the change in drain source current of the second FET by applying an appropriate voltage to the gate of the second FET.
Description:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to voltage regulators. More specifically, the invention relates to a compact voltage regulator which can be used with wireless communications devices.
2. Description of the Related Art
Modern wireless communications devices, such as Code Division Multiple Access (CDMA) telephones and other cellular telephones are held to ever-higher performance standards. Ongoing research work is being performed for communication devices to provide clear and undistorted transmission. To achieve this, linear power amplifiers are used in wireless communication devices. The linear power amplifiers require constant quiescent current through operating conditions to maintain linearity. To provide the constant quiescent current, a regulated voltage is needed.
Usually, a voltage regulator is implemented on a separate die and the regulated voltage is provided to the linear power amplifiers. In mobile phones, the voltage regulator may be a stand alone or integrated with other circuits. The requirement of an additional die increases the manufacturing cost. Therefore, to minimize the cost, there is a need for a compact voltage regulator which may be implemented on the same die as the linear power amplifier.
SUMMARY OF THE INVENTION
An object of the invention is to provide a constant bias current for power amplifier circuits.
Another object of the invention is to generate a regulated voltage independent from load and power supply.
Yet another object of the invention is to generate a regulated voltage with a desired temperature dependency.
Another object of the invention is to provide a compact voltage regulator.
Still another object of the invention is to provide a shutdown switch for the voltage regulator.
To achieve the above objectives, the invention provides a system for voltage regulation. The system includes an error amplifying module, and a regulator. The error amplifying module includes a bipolar junction transistor (BJT), and a diode. The regulator includes a field effect transistor (FET) and a resistor. The BJT amplifies the difference between a reference voltage and a desired value of output voltage (V reg ). The reference voltage V ref is the sum of voltages across the base-emitter junction of BJT, diode and resistor. Further, the reference voltage V ref is generated based on the output voltage, V reg . The regulator regulates the variations in the output voltage, V reg , based on the output of the error amplifying module. In one embodiment of the invention, a switch module is provided. The switch module includes a field effect transistor (FET). The switch module switches the system for voltage regulation in ‘On’ or ‘Off’ states.
The system provides a stable output voltage in case of variations due to power supply and load. The system provides a constant bias current to power amplifier circuits and other circuits which need a temperature defined power supply. Further, the system provides a voltage regulator that may be implemented on a single die, along with the circuit for which voltage is to be regulated. This minimizes the cost of manufacturing. In one embodiment of the invention, if the reference voltage is temperature independent, the system may provide voltage regulation independent of temperature.
BRIEF DESCRIPTION OF THE DRAWINGS
So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to various embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
FIG. 1 is a schematic representation of a circuit diagram of a system for voltage regulation, in accordance with an embodiment of the invention;
FIG. 2 is a schematic representation of a circuit diagram of a system for voltage regulation, in accordance with another embodiment of the invention;
FIG. 3 is a schematic representation of a circuit diagram of a system for voltage regulation with a switch module, in accordance with an embodiment of the invention;
FIG. 4 is a schematic representation of a circuit diagram of a system for voltage regulation with a switch module, in accordance with another embodiment of the invention;
FIG. 5 is a schematic representation of a circuit diagram of a system for voltage regulation with a switch module used with a power amplifier circuit, in accordance with an embodiment of the invention;
FIG. 6 is a schematic representation of a circuit diagram of a system for voltage regulation with a switch module used with a power amplifier circuit, in accordance with an embodiment of the invention;
FIG. 7 is a schematic representation of the circuit diagram of the system for voltage regulation with the switch module used with a power amplifier circuit, in accordance with another embodiment of the invention; and
FIG. 8 is a graph illustrating variations in V reg , the output voltage of the voltage regulator, versus the variations in load and temperature.
DETAILED DESCRIPTION
Various embodiments of the invention provide a low power system for voltage regulation. The system for voltage regulation is, hereinafter, referred to as a voltage regulator. The voltage regulator includes an error amplifying module and a regulator. The error amplifying module amplifies the difference between a reference voltage and a desired value of an output voltage. The reference voltage is based on the output voltage to be regulated. The regulator regulates the output voltage based on the output of the error amplifying module. The voltage regulator further includes a switch module to set the voltage regulator in ‘On’ or ‘Off’ state.
FIG. 1 is a schematic representation of a circuit diagram of a voltage regulator 100 , in accordance with an embodiment of the invention. Voltage regulator 100 includes an error amplifying module 102 and a regulator 104 . Error amplifying module 102 includes a diode D 1 , a Bipolar Junction Transistor (BJT) Q 1 , and a resistor R 2 . Regulator 104 includes a Field Effect Transistor (FET) Q 2 , and a resistor R 1 . Diode D 1 is connected between the source of FET Q 2 and base of Q 1 . Resistor R 2 is connected in series between the emitter of BJT Q 1 and ground. Resistor R 1 is connected between the gate and source of FET Q 2 . The collector of BJT Q 1 is connected to the gate of FET Q 2 . Further, regulator 104 is connected to a battery, V bat . V bat provides the necessary power required by voltage regulator 100 to operate.
BJT Q 1 amplifies the difference between a reference voltage V ref and a desired value of an output voltage V reg . V ref is the sum of the voltages across diode D 1 , the base-emitter junction of BJT Q 1 and resistor R 2 . Regulator 104 regulates variations in V reg , also referred to as regulated voltage, based on the amplified difference between V reg and V ref . Regulator 104 regulates V reg by adjusting a current I reg flowing through voltage regulator 100 . I reg is the drain-source current, I ds , of FET Q 2 . In one embodiment of the invention, V reg is equal to V ref .
I reg flowing through voltage regulator 100 is the sum of a collector current, I c , and a base current, 1 b , of BJT Q 1 . In an embodiment of the invention, the value of I b is less than that of I c and therefore may be ignored. Therefore, I reg may be considered to be equal to collector current I c . Hence, a variation in the value of I c causes a variation in I ds , which further causes variations in I reg . The value of V reg is maintained by FET Q 2 through the voltage drop across resistor R 1 . In one embodiment of the invention, variations in V reg may be caused by variation in load, temperature and voltage V bat .
In one embodiment of the invention, if V reg exceeds a desired value, base current, I b , and collector current Ic of BJT Q 1 increases. Higher I c results in higher voltage drop across resistor R 1 . This makes the gate-source voltage of FET Q 2 more negative, thereby resulting in lower drain source current, I ds , and subsequently reducing V reg .
In another embodiment of the invention, if V reg drops below the desired value, the voltage across the base-emitter junction of BJT Q 1 and resistance R 2 decreases. Due to the decrease in the voltage across the base-emitter junction of BJT Q 1 , its collector current I c reduces. As a result, the voltage drop across resistor R 1 reduces. This makes the gate-source voltage of FET Q 2 less negative, thereby increasing I ds . The increase in I ds results in higher I reg , thereby increasing V reg .
In one embodiment of the invention, BJT Q 1 is a Heterojunction Bipolar Transistor (HBT). In various embodiments of the invention, BJT Q 1 may be replaced by any transistor amplifier such as, an operational amplifier, a differential amplifier and the like. In one embodiment of the invention, FET Q 2 is a Pseudomorphic High Electron Mobility Transistor (pHEMT). In various embodiments of the invention, FET Q 2 is a depletion mode type field effect transistor. In one embodiment of the invention, the value of resistor R 2 may be set to zero. The reference voltage, in this case, is the sum of voltages across diode D 1 and base-emitter junction of BJT Q 1 . In various embodiments of the invention, FET Q 2 is used as an amplifier.
Diode D 1 and emitter-base junction of BJT Q 1 provides a temperature coefficient to voltage regulator 100 , the temperature coefficient being the change in output voltage, V reg , of the voltage regulator 100 per degree centigrade change. Based on the temperature coefficients of the selected components, a regulated voltage with desired temperature dependency may be generated. In various embodiments of the invention, a regulated voltage with desired temperature dependency may be required to provide a specified quiescent current for power amplifier circuits.
In one embodiment of the invention, a parallel combination of a resistor and diode D 1 may be implemented in place of diode D 1 (not shown) to set the temperature coefficient of V reg . In another embodiment of the invention, a series combination of a resistor (not shown) and diode D 1 may be implemented in place of diode D 1 . In still another embodiment of the invention, diode D 1 may be replaced by a resistor. In an embodiment of the invention, a Zener diode may be used instead of diode D 1 . In such a case, an additional resistor is connected between the base of BJT Q 1 and ground. The additional resistor supplies the required current to bring the Zener diode into its operating range.
In various embodiments of the invention, the configuration of the components used in voltage regulator 100 , like BJT Q 1 , FET Q 2 , diode D 1 , may be selected with respect to the circuit for which voltage regulation is required.
FIG. 2 is a schematic representation of a circuit diagram of a voltage regulator 202 , in accordance with another embodiment of the invention. Voltage regulator 202 includes an error amplifying module 204 and a regulator 206 . Error amplifying module 204 includes an amplifier A 1 , a BJT Q 1 , a diode D 1 and the resistors R 2 , R 3 , R 4 , and R 5 . Regulator 206 includes a field-effect transistor (FET) Q 2 and resistor R 1 . One input of amplifier A 1 is connected to collector of BJT Q 1 and other input is connected between resistor R 4 and resistor R 5 . Output of amplifier A 1 is connected to gate of FET Q 2 . Resistor R 1 is connected between gate and source of FET Q 2 . Diode D 1 is connected between source of Q 2 and base of Q 1 of BJT Q 1 . Resistor R 2 is connected to emitter of BJT Q 1 and the other end of resistor R 2 is grounded. One end of resistor R 4 is connected to source of FET Q 2 and to one end of resistor R 5 . The other end of resistor R 5 is grounded. A sample of voltage, V reg through the resistive divider made with resistor R 4 and resistor R 5 , is provided to the amplifier A 1 . Amplifier A 1 provides additional amplification of the difference between the actual value of the output voltage and the desired voltage value. The additional amplification provides more stability to voltage regulator 202 against variations caused by battery voltage and load. Regulator 206 regulates the output voltage V reg based on the output of the amplifier A 1 . In one embodiment of the invention, amplifier A 1 may be a differential amplifier. In another embodiment of the invention, amplifier A 1 may be an operational amplifier.
FIG. 3 is a schematic representation of a circuit diagram of voltage regulator 100 with a switch module 302 , in accordance with an embodiment of the invention. Switch module 302 includes a field effect transistor (FET) Q 3 , and a resistor R 6 . Resistor R 6 is connected to the gate of FET Q 3 . A DC supply battery, V enable , provides a control voltage to switch module 302 and controls the functioning of switch module 302 . Further, battery, V bat , supplies the required power to switch module 302 and to voltage regulator 100 .
Switch module 302 turns voltage regulator 100 ‘On’ and ‘Off’. In one embodiment of the invention, when the value of V enable is ‘High’, i.e., when the value of V enable is equal to the operating voltage of FET Q 3 , switch module 302 turns voltage regulator 100 to ‘On’ state. In ‘On’ state switch module 302 passes drain current, I ds , into FET Q 2 , thereby allowing voltage regulator 100 to function. In another embodiment of the invention, voltage supplied by V enable is ‘Low’, i.e., V enable is adjusted such that no current flows through FET Q 3 and voltage regulator 100 . This switches voltage regulator 100 to ‘Off’ state.
FIG. 4 is a schematic representation of a circuit diagram of a voltage regulator 402 with switch module 302 , in accordance with another embodiment of the invention. Voltage regulator 402 includes an error amplifying module 404 and a regulator 406 . Switch module 302 is same as described in FIG. 3. Error amplifying module 404 includes a resistor R 7 , a Bipolar Transistor (BJT) Q 1 , and a resistor R 2 . Regulator 406 is similar to regulator 104 as described in FIG. 1. Resistor R 7 is connected between the base of BJT Q 1 and source of Q 2 . Resistor R 2 is connected between emitter junction of BJT Q 1 and ground. The use of resistor R 7 instead of diode D 1 , as shown in FIG. 1, FIG. 2 and FIG. 3, results in a lower temperature dependency of V reg , as the reference voltage includes only one temperature dependent element, which is base-emitter junction of BJT Q 1 . In one embodiment of the invention, value of resistors R 2 and/or R 7 may be set to zero.
Voltage regulator 100 , as described in FIG. 1, FIG. 2 and FIG. 3, may be used with current mirror based bias circuits to provide constant, temperature compensated biasing current to the transistors. The temperature coefficient of output voltage of voltage regulator 100 is based on diode D 1 and base-emitter junction of BJT Q 1 . Further, it keeps the bias current approximately constant with respect to temperature. The use of voltage regulator 100 for providing constant biasing current to transistors is depicted in FIG. 5 and FIG. 6.
FIG. 5 is a schematic representation of a circuit diagram of voltage regulator 100 with switch module 302 being used with a power amplifier 502 , in accordance with an embodiment of the invention. Voltage regulator 100 and switch module 302 are connected to power amplifier 502 through a current mirror 504 . Power amplifier 502 includes a BJT Q 6 , capacitors C 1 and C 2 , and an inductor L 1 . BJT Q 6 , capacitors C 1 and C 2 , and inductor L 1 are connected as shown in FIG. 5. Current mirror 504 includes BJTs Q 4 and Q 5 , resistors R 8 , R 9 and R 10 . BJTs Q 4 and Q 5 and resistors R 8 , R 9 and R 10 are connected as shown in FIG. 5. Voltage regulator 100 provides output voltage to current mirror 504 . This output voltage is power supply and load regulated, but is temperature dependent. The temperature coefficient of output voltage of voltage regulator 100 is similar to that of BJT Q 6 of power amplifier 502 and current mirror 504 combined.
FIG. 6 is a schematic representation of the circuit diagram of a voltage regulator 100 with switch module 302 used with a power amplifier 502 , in accordance with an embodiment of the invention. Power amplifier 502 is same as described in FIG. 5. Voltage regulator 100 is connected to power amplifier 502 through resistor R 11 . Voltage regulator 100 , as described in FIG. 3 may be used to set quiescent current of a low power transistor Q 6 , without using current mirror 504 . The output voltage of voltage regulator 100 is similar to that of the base-emitter junction of BJT Q 1 , and has the desired temperature coefficient.
FIG. 7 is a schematic representation of a circuit diagram of voltage regulator 100 with switch module 302 being used with power amplifier circuit 502 , in accordance with another embodiment of the invention. Voltage regulator 100 is connected to power amplifier circuit 502 through a current mirror circuit 702 . Current mirror circuit 702 includes BJT Q 4 , FET Q 7 , diode D 2 , resistors R 8 , R 9 and R 10 . BJT Q 5 shown in current mirror 504 is replaced by FET Q 7 and diode D 2 . Voltage regulator 100 is connected to current mirror circuit 702 through a resistor R 8 . BJT Q 4 , FET Q 7 , diode D 2 , resistors R 8 , R 9 and R 10 are connected as shown in FIG. 7. Source of FET Q 7 and resistor R 10 are connected to power amplifier circuit 502 . BJT Q 6 , capacitors C 1 and C 2 , and inductor L 1 are connected as shown in FIG. 7.
FIG. 8 is a graph illustrating variations in V reg , the output voltage of voltage regulator 100 (V reg ), (in Volts), versus the variations in load current (in milli-Amperes) with temperature. Load current I_load represents the variations caused by load. The graph is generated using the following specifications of the circuit elements of voltage regulator 100 of FIG. 1. The value of resistor R 1 is equal to 330 Ohm and resistor R 2 is equal to zero. The value of the emitter area of diode D 1 is equal to 14 μm 2 . Further, the value of the emitter area of Q 1 is equal to 14 μm 2 and the width of Q 2 is equal to 500 μm. Line A shows the variance in desired voltage, V reg (from 2.688 Volts to 2.679 Volts), due to change in load current, I_load (from 0.1 mA to 5 mA) at a temperature of −30° C. Line B shows variance in V reg (from 2.611 Volts to 2.601 Volts), due to change in I_load (from 0.1 mA to 5 mA) at a temperature of 25° C. Line C shows variance in V reg (from 2.494 Volts to 2.482 Volts), due to change in I_load (from 0.1 mA to 5 mA) at a temperature of 110° C.
The voltage regulator as explained above has a number of advantages. Voltage regulator provides stable voltage in case of variations in power supply and load. The voltage regulator provides a desired temperature coefficient. The voltage regulator may be implemented on a single die along with the circuit for which voltage needs to be regulated. Further, the voltage regulator includes a shutdown switch, which allows the voltage regulator to be switched ‘On’ and ‘Off’ with negligible leakage. Moreover, the voltage regulator draws less current for providing the desired voltage regulation.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised (such as by interchanging the source drain terminations where the FETs used are symmetrical devices) without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.